Nitrate determination in waters is generally carried out with cadmium filings and carcinogenic reagents or by reaction with phenolic
compounds in highly concentrated sulfuric acid medium. In this work, it was developed a green analytical procedure for nitrate determination
in natural waters based on direct spectrophotometric measurements in ultraviolet, using a flow-injection system with an anion-exchange
column for separation of nitrate from interfering species. The proposed method employs only one reagent (HClO4) in a minimum amount
(equivalent to 18L concentrated acid per determination), and allowed nitrate determination within 0.50–25.0 mg L
−1
, without interference
of up to 200.0 mg L
−1
humic acid; 1.0 mg L
−1
NO2
−
; 200.0 mg L
−1
PO4
3−
; 75.0 mg L
−1
Cl
−
; 50.0 mg L
−1
SO4
2−
and 15.0 mg L
−1
Fe
3+
. The
detection limit (99.7% confidence level) and the coefficient of variation (n= 20) were estimated as 0.1 mg L
−1
and 0.7%, respectively. The
results obtained for natural water samples were in agreement with those achieved by the reference method based on nitrate reduction with
copperized cadmium at the 95% confidence level.
© 2004 Elsevier B.V. All rights reserved.